This is only a preview of the February 2004 issue of Silicon Chip. You can view 35 of the 96 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Articles in this series:
Items relevant to "Simple Supply Rail Monitor For PCs":
Items relevant to "Studio 350 Power Amplifier Module; Pt.2":
Items relevant to "Using The Valve Preamp In A Hifi System":
Articles in this series:
Purchase a printed copy of this issue for $10.00. |
25 YEARS OF
AUTOMOTIVE
ABS
by Julian Edgar
Anti-Lock Braking Systems (ABS) are now a quarter of a
century old. In that time the systems have saved countless
dollars in panel damage, a huge number of injuries and
prevented many deaths. German company Bosch has been
instrumental in developing the technology and seeing it
widely adopted by car manufacturers around the world.
Here we take a look at the development.
36 Silicon Chip
www.siliconchip.com.au
Bosch ABS
Milestones
1936: Bosch registers a patent for a
“mechanism to prevent locking of the wheels of a motor
vehicle”.
1970: ABS 1 models perform all
required functions; but
reliability of the control unit
is not yet adequate.
1978: First fitting of ABS 2 as option
at Mercedes-Benz and shortly
thereafter at BMW.
As the first ‘active’ car control system with major implications for safety,
ABS required extensive development prior to its release. Here early vehicle
testing by Bosch is shown.
1981: 100,000th ABS system
supplied; ABS now also in
commercial vehicles.
1985: Bosch ABS fitted for the first
time in U.S. vehicles.
In the 25 years
since Bosch
ABS went into
production, the
mass of the control
system has dropped
from 6.3 to 1.6kg,
the number of
components in the
Electronic Control
Unit has dropped
from 140 to 16,
and the amount of
memory has risen
from 2 to 128kB!
1986: One million Bosch ABS
delivered.
1987: Production of Traction Control
System (TCS) for passenger
cars starts.
1989: With the ABS 2E, the control
unit is attached directly to the
hydraulic unit.
1992: 10 million ABS systems from
Bosch.
1993: Start of production of ABS 5.0
from Bosch.
1995: Production of Bosch ABS 5.3
starts (with attached microhybrid control unit); production start of Electronic Stability
Control.
While slow
to gather
momentum, the
proportion of
new cars sold
worldwide with
ABS as standard
has skyrocketed
over the last 15
years. Just under
70 per cent of all
new cars now
have ABS as
standard.
www.siliconchip.com.au
1998: Bosch begins volume production of ABS 5.7
1999: 50 million Bosch ABS systems.
2001: Bosch ABS version 8 launched.
2003: 25 years of series production
of Bosch ABS
February 2004 37
CONTROL UNIT HISTORY
1970
Bosch subsidiary Teldix started working on ABS in 1964 and by
1970 had developed a system controlled entirely by electronics.
The basic structure of this design, named ABS 1, is still to
be found in nearly all ABS systems. But the reliability and
durability of the electronic control unit - with its roughly 1000
analog components and the safety switches - were not good
enough for volume production.
1978
The advent of digital technology and integrated control circuits
allowed the number of electronic components to be reduced
to 140. After 14 long years of development, everything was
finally in place in 1978: the second generation of Bosch’s ABS
– ABS 2 – began to be fitted as optional equipment, at first
in Mercedes-Benz’s ‘S’-class cars and shortly afterwards in
BMW’s 7-series vehicles.
1983
Based on the first ABS, the following 1983 generation 2S was
more compact and efficient. However still only 0.3 per cent of
new vehicles worldwide were then being fitted with ABS.
1987
In 1987, Bosch produced the first traction control system
(TCS) for passenger vehicles. It was based on ABS2S and was
upgraded with the required hydraulics and electronic elements.
TCS helps to improve acceleration on smooth or slippery
surfaces, and also increases stability by reducing engine power
when corners are taken too fast.
1989
In 1989, Bosch started
the mass production of
ABS 2E. For the first time,
developers succeeded in
integrating a control unit
ECU manufactured in hybrid
technology.
Bosch Not the First
1993
More compact and powerful
solenoid valves are
characteristic of the 1993
generation 5 ABS. The
integrated electronic control
unit ECU also had more
functions.
38 Silicon Chip
Despite Bosch developing the
technology that has allows ABS
to be implemented in millions of
cars, it was not the first company
to be involved in fitting ABS to a
passenger car.
The first car with ABS was the
1966-71 Jensen Interceptor FF,
which used Dunlop Maxaret antilock brakes originally developed for
fighter aircraft landing on aircraft
carriers.
www.siliconchip.com.au
1995
The 1995 ABS 5.3 was the first
to be fitted with an ECU in
micro hybrid technology. Total
weight and size were further
reduced.
1998
2001
1978
The brake control system
of the 1998 generation 5.7
is optimised for the use in
Electronic Stability Control
systems.
2001
The direct comparison of
hydraulic and electronic
control units in the ABS2 from
1978 (left) and the integrated
ABS8 of the latest generation
show how the latter is much
more compact.
ABS 8 – the current generation
– first appeared in 2001.
It uses a modular design,
which allows various degrees
of complexity of the brake
control system – ABS, Traction
Control and Electronic
Stability – to be manufactured
in very similar ways.
How ABS Works
The hydraulic unit is the central component of an ABS
system. Each of the four wheels has a speed sensor, which
measures the rotational speed of the wheel. This
information is monitored by an electronic control unit,
which opens and closes the magnetic valves in the hydraulic
unit at the right time.
If a wheel is about to lock under heavy braking, the system
reduces the hydraulic pressure on that particular wheel until the
threat of locking is past. Once the wheel is turning freely again,
the hydraulic pressure is increased. This variation in pressure
continues until the driver reduces the force on the brake pedal or
until the tendency to lock is overcome – when there is more grip
on the road surface, for instance. Depending on the particular system,
there is a certain amount of feedback movement at the brake pedal.
www.siliconchip.com.au
sc
February 2004 39
|